The present invention generally relates to an apparatus for fabricating a semiconductor device by using plasma and a method for fabricating the semiconductor device, and more particularly relates to measures taken for preventing particles from depositing on an object to be processed.
Plasma processing is currently utilized at various stages in the fabrication of a semiconductor device. It is known that particles such as reactants are generated during the plasma processing. For example, such reactants are generated as a result of the decomposition of a source gas, the reaction between the source gas and an object to be processed (e.g., a semiconductor substrate) and the like. Although many of these particles are pumped out of the reaction chamber through an exhaust port along with the gas, part of the particles are deposited on the substrate processed, thereby deteriorating the properties of the substrate in various respects. The deposition of such particles plays a significant role in causing various defects in semiconductor devices. Accordingly, in order to increase the yield of semiconductor devices, it is desirable to fabricate the devices by taking every measure to prevent contaminants, such as particles, from being deposited on the surface of a substrate during a fabrication process.
In view of this demand, many techniques have heretofore been suggested as to the measures taken to control the generation of particles such as reactants during plasma processing or to prevent such particles from being deposited on a substrate. However, under current circumstances, these problems have not been drastically solved yet by any of those techniques. Considering the status of semiconductor devices in the art as the object of everlasting miniaturization and higher-than-ever integration, the significance of such measures for preventing the deposition of particles will continue to increase day after day.
It is taught that the particles generated in plasma are trapped in the vicinity of the interface between a plasma sheath and a plasma glow region in a reaction chamber (see T. Fukuzawa et al., Jpn. J. Appl. Phys., 33, 4212 (1994)). Also, in using an etching apparatus, when the etching process is completed and plasma is extinguished, the particles, which have been trapped in the vicinity of the interface between the plasma sheath and the plasma glow region, undesirably fall onto a substrate, thereby decreasing the yield of devices.
In view of the above-described problems, the present invention was made to increase the yield of an object by taking various measures for preventing the particles, which are trapped in the vicinity of the interface between a plasma sheath and a plasma glow region, from falling onto a substrate in an apparatus for fabricating a semiconductor device by utilizing plasma.
A first apparatus for fabricating a semiconductor device according to the present invention includes: a reaction chamber in which an object to be processed is positioned and subjected to plasma processing; plasma generating means for generating plasma regions above a region where the object is positioned in the reaction chamber, the plasma regions including a plasma glow region and a plasma sheath underlying the plasma glow region; at least one exhaust pipe having an opening in the vicinity of the interface between the plasma glow region and the plasma sheath; and exhaust means interposed in the exhaust pipe.
In this apparatus, as the plasma processing proceeds, particles such as reactants are once trapped in the vicinity of the interface between the plasma glow region and the plasma sheath, but are then exhausted through the opening of the exhaust pipe. Thus, when the plasma regions are extinguished, a smaller number of particles are present in the vicinity of the interface between the plasma glow region and the plasma sheath. Accordingly, it is possible to suppress the deposition of particles on an object to be processed.
In one embodiment of the present invention, the openings of the exhaust pipes are preferably provided so as to surround the outer periphery of the interface between the plasma glow region and the plasma sheath.
In such an embodiment, the number of particles can be reduced even more effectively.
A second apparatus for fabricating a semiconductor device according to the present invention includes: a reaction chamber in which an object to be processed is positioned and subjected to plasma processing; plasma generating means for generating plasma regions above a region where the object is positioned in the reaction chamber, the plasma regions including a plasma glow region and a plasma sheath underlying the plasma glow region; and a dust-collecting electrode disposed in the vicinity of the interface between the plasma glow region and the plasma sheath and biased at a positive potential.
In this apparatus, as the plasma processing proceeds, particles, such as reactants, being negatively charged are once trapped in the vicinity of the interface between the plasma glow region and the plasma sheath, but are then collected to the dust-collecting electrode biased at a positive potential. Thus, when the plasma regions are extinguished, a smaller number of particles exist in the vicinity of the interface between the plasma glow region and the plasma sheath. Accordingly, it is possible to suppress the deposition of particles on an object to be processed.
In one embodiment of the present invention, the dust-collecting electrodes are preferably disposed so as to surround the outer periphery of the interface between the plasma glow region and the plasma sheath.
In such an embodiment, the number of particles can be reduced even more effectively.
In another embodiment of the present invention, the apparatus preferably further includes: an exhaust pipe having an opening on the outer side of the dust-collecting electrode; and exhaust means interposed in the exhaust pipe.
In such an embodiment, since the particles collected in the dust-collecting electrode are exhausted through the exhaust pipe, the number of particles present in the entire reaction chamber can be reduced and the deposition of the particles on the object can be suppressed.
A third apparatus for fabricating a semiconductor device according to the present invention includes: a reaction chamber in which an object to be processed is positioned and subjected to plasma processing; plasma generating means for generating plasma regions above a region where the object is positioned in the reaction chamber, the plasma regions including a plasma glow region and a plasma sheath underlying the plasma glow region; light-collecting means, which is disposed in the vicinity of the interface between the plasma glow region and the plasma sheath and has a focus at a position inner to one end of the region where the object is positioned; and light-irradiating means for irradiating light on the light-collecting means.
In this apparatus, as the plasma processing proceeds, particles such as reactants are once trapped in the vicinity of the interface between the plasma glow region and the plasma sheath, but are then moved out of the region where the object is positioned owing to the function of the light-collecting means. Thus, when the plasma regions are extinguished, a smaller number of particles are present in the vicinity of the interface between the plasma glow region and the plasma sheath. Accordingly, it is possible to suppress the deposition of particles on an object to be processed.
In one embodiment of the present invention, the position of the focus is preferably movable in the direction of the diameter of the object by controlling the light-collecting means and the light-irradiating means.
In such an embodiment, the particles can be removed with more certainty.
In another embodiment of the present invention, multiple pairs of the light-collecting means and the light-irradiating means are preferably disposed so as to surround the outer periphery of the interface between the plasma glow region and the plasma sheath.
In such an embodiment, the deposition of the particles can be suppressed even more effectively.
In still another embodiment of the present invention, an exhaust port for exhausting a gas out of the reaction chamber is preferably provided below the light-collecting means.
In such an embodiment, the particles, which have been moved out of the region where the object is positioned, can be rapidly exhausted through the exhaust port. Thus, the number of particles present in the entire reaction chamber can be reduced rapidly and the deposition of the particles on the object can be suppressed even more effectively.
In still another embodiment, the plasma generating means may be a capacitively coupled plasma apparatus.
In still another embodiment, the plasma generating means may be a microwave resonance plasma apparatus.
In still another embodiment, the plasma generating means may be an inductively coupled plasma apparatus.
In still another embodiment, the plasma generating means may be a helicon wave plasma apparatus.
A method for fabricating a semiconductor device according to the present invention includes the steps of: positioning an object to be processed in a reaction chamber for performing plasma processing on the object; generating plasma regions above a region where the object is positioned in the reaction chamber, the plasma regions including a plasma glow region and a plasma sheath underlying the plasma glow region; and moving particles such as plasma reactants, which are trapped in the vicinity of the interface between the plasma glow region and the plasma sheath, to the outside of a region overlying the region where the object is positioned.
In accordance with this method, as the plasma processing proceeds, particles such as reactants are once trapped in the vicinity of the interface between the plasma glow region and the plasma sheath, but are then collected out of the region where the object is positioned. Thus, when the plasma regions are extinguished, a smaller number of particles are present in the vicinity of the interface between the plasma glow region and the plasma sheath. Accordingly, it is possible to suppress the deposition of particles on an object to be processed.
In one embodiment of the present invention, the method preferably further includes the step of exhausting the particles out of the reaction chamber.
In such an embodiment, since the particles, which have been moved out of the region where the object is positioned, can be rapidly exhausted out of the reaction chamber. Thus, the number of particles present in the entire reaction chamber can be reduced rapidly and the deposition of the particles on the object can be suppressed even more effectively.